Discrimination between poultry eggs on the basis of some observable quality is a well-known and long-used practice in the poultry industry. “Candling” is a common name for one such technique, a term which has its roots in the original practice of inspecting an egg using the light from a candle. As is known to those familiar with eggs, although egg shells appear opaque under most lighting conditions, they are in reality somewhat translucent, and when placed in front of direct light, the contents of the egg can be observed.
Eggs which are to be hatched to live poultry are typically candled during embryonic development to identify clear, rotted, and dead eggs (collectively referred to herein as “non-live eggs”). Non-live eggs are removed from incubation to increase available incubator space. In many instances it is desirable to introduce a substance, via in ovo injection, into a live egg prior to hatch. Injections of various substances into avian eggs are employed in the commercial poultry industry to decrease post-hatch mortality rates or increase the growth rates of the hatched bird. Examples of substances that have been used for, or proposed for, in ovo injection include vaccines, antibiotics and vitamins. Examples of in ovo treatment substances and methods of in ovo injection are described in U.S. Pat. No. 4,458,630 to Sharma et al. and U.S. Pat. No. 5,028,421 to Fredericksen et al.
In ovo injections of substances typically occur by piercing an egg shell to create a hole therethrough (e.g., using a punch or drill), extending an injection needle through the hole and into the interior of the egg (and in some cases into the avian embryo contained therein), and injecting one or more treatment substances through the needle. An example of an injection device is disclosed in U.S. Pat. No. 4,681,063 to Hebrank; this device positions an egg and an injection needle in a fixed relationship to each other, and is designed for the high-speed automated injection of a plurality of eggs. The selection of both the site and time of injection treatment can also impact the effectiveness of the injected substance, as well as the mortality rate of the injected eggs or treated embryos. See, for example, U.S. Pat. No. 4,458,630 to Sharma et al., U.S. Pat. No. 4,681,063 to Hebrank, and U.S. Pat. No. 5,158,038 to Sheeks et al.
In commercial poultry production, only about 60% to 90% of commercial broiler eggs hatch. Eggs that do not hatch include eggs that were not fertilized, as well as fertilized eggs that have died. Infertile eggs may comprise from about 5% up to about 25% of all eggs in a set. Due to the number of non-live eggs encountered in commercial poultry production, the increasing use of automated methods for in ovo injection, and the cost of treatment substances, an automated method for identifying live eggs and selectively injecting only live eggs, is desirable.
U.S. Pat. No. 3,616,262 to Coady et al. discloses a conveying apparatus for eggs that includes a candling station and an inoculation station. At the candling station, light is projected through the eggs and assessed by a human operator, who marks any eggs considered non-live. Non-live eggs are manually removed before the eggs are conveyed to the inoculating station.
An egg may be a “live” egg, meaning that it has a viable embryo. FIG. 1A illustrates a live poultry egg 1 at about day one of incubation. FIG. 1B illustrates the live egg 1 at about day eleven of incubation. The egg 1 has a somewhat narrow end in the vicinity represented at 1a as well as an oppositely disposed broadened end portion in the vicinity shown at 1b. In FIG. 1A, an embryo 2 is represented atop the yolk 3. The egg 1 contains an air cell 4 adjacent the broadened end 1b. As illustrated in FIG. 1B, the wings 5, legs 6, and beak 7 of a baby chick have developed.
An egg may be a “clear” or “infertile” egg, meaning that it does not have an embryo. More particularly, a “clear” egg is an infertile egg that has not rotted. An egg may be an “early dead” egg, meaning that it has an embryo which died at about one to five days old. An egg may be a “mid-dead” egg, meaning that it has an embryo which died at about five to fifteen days old. An egg may be a “late-dead” egg, meaning that it has an embryo which died at about fifteen to eighteen days old.
An egg may be a “rotted” egg, meaning that the egg includes a rotted infertile yolk (for example, as a result of a crack in the egg's shell) or, alternatively, a rotted, dead embryo. While an “early dead”, “mid-dead” or “late-dead egg” may be a rotted egg, those terms as used herein refer to such eggs which have not rotted. Clear, early-dead, mid-dead, late-dead, and rotted eggs may also be categorized as “non-live” eggs because they do not include a living embryo.
There are other applications where it is important to be able to distinguish between live and non-live eggs. One of these applications is the cultivation and harvesting of vaccines via live eggs (referred to as “vaccine production eggs”). For example, human flu vaccine production is accomplished by injecting seed virus into a chicken egg at about day eleven of embryonic development (Day-11 egg), allowing the virus to grow for about two days, euthanizing the embryo by cooling the egg, and then harvesting the agnostic fluid from the egg. Typically, eggs are candled before injection of a seed virus to remove non-live eggs. Vaccine production eggs may be candled one or more days prior to injection of a seed virus therein. Identification of live eggs in vaccine production is important because it is desirable to prevent seed vaccine from being wasted in non-live eggs and to reduce costs associated with transporting and disposing of non-live eggs.
U.S. Pat. Nos. 4,955,728 and 4,914,672, both to Hebrank, describe a candling apparatus that uses infrared detectors and the infrared radiation emitted from an egg to distinguish live from infertile eggs. U.S. Pat. No. 4,671,652 to van Asselt et al. describes a candling apparatus in which a plurality of light sources and corresponding light detectors are mounted in an array, and wherein eggs are passed on a flat between the light sources and the light detectors.
Unfortunately, conventional candling techniques may have somewhat limited accuracy, especially at high candling through-put speeds. Pulsed light opacity identification systems can operate at speeds equivalent to about 300,000 eggs per hour and successfully identify clear eggs from a stream of eggs. However, some eggs identified as being live will in fact be non-live (e.g., rotted eggs, mid and late dead eggs).
Thermal-based candling systems can detect rotted eggs in egg streams of up to 50,000 eggs per hour. Unfortunately, because of egg-to-egg thermal variations, thermal-based candling systems may misidentify live and non-live eggs. In addition, thermal-based candling systems may not be accurate with embryos that generate less heat than day 17 eggs.
Embryo heartbeat (pulse) detection methods are known that can detect live eggs with a high degree of accuracy. For example, Buddy by Avitronics (Truro, England) can detect avian embryo heartbeats. Detection happens in about five to ten seconds for about 60% of eggs, with near 100% detection requiring 60 second sampling times. Unfortunately, the time required to detect a live egg is prohibitively slow for use in hatcheries where high through-put rates are required. For automated pulse detection to be a useful method of determining viable eggs, a much shorter processing time is needed to read hatchery volumes of eggs (typically several hundred thousand in six to eight hours).
U.S. Pat. No. 5,173,737 to Mitchell describes a method of determining whether an egg contains a live embryo by directing light into an egg to stimulate embryo movement, and then measuring resulting embryo movement. Unfortunately, the Mitchell method may be time-consuming and may not accurately detect live embryos that do not move as a result of light stimulation.